In the cloud computing market, there are a handful of major vendors. Most agree Amazon Web Services is a market leader on the infrastructure as a service (IaaS) side, but Microsoft, Google and younger companies like Joyent are looking to dethrone AWS. And then there's OpenStack, which is for almost everyone else.

An open source cloud management platform for public or private clouds, OpenStack has spent the last two and a half years building up an impressive resume of companies that have singed on as backers. From HP, Dell, Cisco, IBM, Rackspace and others have all hitched their wagons to OpenStack. Now, the question for 2013, experts say, is seeing if customer adoption of the platform rises to the same level of interest that the vendors have showed in embracing the technology.

Vendors are taking different approaches to their involvement in OpenStack. Some, like Rackspace and HP, have built their public cloud computing product based on OpenStack code; Dell has committed to doing this strategy as well. Others, like Linux distribution companies Red Hat, Canonical and SUSE, are all each working on their own supported distributions of OpenStack code in 2013 for end users to build private clouds. These moves are expected to extend the user base of OpenStack beyond the initial use cases already seen in the market.

The promise of OpenStack is to provide an open source cloud platform that both end users and service providers can use that will give Amazon Web Services a run for its money. OpenStack backers say having a common cloud platform like OpenStack that powers both internal private clouds for users, as well as the public clouds from service providers will foster an ecosystem where customers will have the freedom to move their applications and workloads between their public and private clouds, and across to multiple vendors. The project is not quite there yet, though. Some, such as Gartner's Lydia Leong caution users to not expect such lofty expectations. She argues that interoperability between public and private OpenStack clouds is not inherent, for example.

But, the fact is OpenStack is growing. At the project's last summit in the fall of 2012, officials said that since the project launched it has expanded from 30,000 lines of code to now more than 600,000. More than 600 developers are working on the project, with more than 400 contributing to it within the last year.

2013 will be an important year for OpenStack, says Forrester cloud analyst James Staten. The vendor community for OpenStack has basically been ironed out; everyone knows who's in and who's out. Now, these vendors are going from planning their OpenStack strategies to executing them, and specifically looking for customer adoption. "There are a lot of companies that have committed to OpenStack but they're not making money on it yet," Staten says.

To make money these vendors need to be selling products though. Rackspace seems the most mature in its OpenStack powered cloud. As one of the original founding members of OpenStack, the company has continued to be a leader in the project and now is one of the first to roll out new features added to the OpenStack code in its commercial offering. HP has made its public cloud generally available, while Red Hat, Dell, IBM and a variety of smaller companies like Nimbula - which is founded by OpenStack pioneer Chris Kemp - are all expected to make major OpenStack product news in 2013.

In addition to this ecosystem of vendors and users coalescing around OpenStack, the project's code continues to mature as well. Twice a year OpenStack holds a design summit in which more than a thousand developers, users, vendors and cloud-watchers gather to discuss the latest trends in OpenStack and plan for the project's next bi-annual release. The latest Folsom release added a virtual networking component named Quantum, which was developed by software defined networking company Nicira, now owned by VMware. The project's Grizzly release, the seventh code release since it was founded in 2010, is expected in April 2013, with another code release slated for late 2013. Recent reports have hinted that identity and access management, as well as supporting multiple cloud platforms from OpenStack's management portal could be in the works for the Grizzly release.

There are some concerns for this project though. Perhaps chief among them is a perception by some that it is simply a marketing project by some of these big-name vendors and that users have not been drawn to the project as fast as the vendors. Staten, the analyst, says it is early enough in the project's development that adoption can still take off.

Another vulnerability could be more mature offerings on the market. VMware, for example, has an extremely mature and widely-used public and private cloud platforms in vSphere and vCloud Director. Microsoft is looking to do the same with its combination of WindowsServer 2012 and its Azure public cloud platform. And then there's Amazon Web Services. Can OpenStack-backed service providers bite into AWS's market share and will users trust a still-developing open source project compared to Amazon's massively scalable cloud? Perhaps 2013 will be the year when answers to some of these questions will become clearer.

Senior Writer Brandon Butler covers the cloud computing industry for Network World by focusing on the advancements of major players in the industry, tracking end user deployments and keeping tabs on the hottest new startups. He contributes to NetworkWorld.com and is the author of the Cloud Chronicles blog. Email him at bbutler@nww.com and follow him on Twitter @BButlerNWW.